This invention relates to an apparatus for and method of manufacturing a bulb including pairs of lead-in wires arranged, in a straight line, respective paired lead-in wires supporting a pair of filaments and locating the filaments at substantially the same height.
For example, a semi-sealed lamp used as a head lamp of an automobile is composed of a reflector covered with a lens in front and a halogen lamp fitted in the reflector. Normally, the semi-sealed lamp is designed so as to be able to emit two beams, pass-by beam and running beam, so that the halogen lamp has a pair of filaments, one for pass-by beam and one for running beam, contained in its glass bulb.
Since the bulb wall temperature of the halogen lamp becomes extremely high when the lamp glows, high-melting-point glass such as silica glass is used for the bulb, and the sealed portion is pinch-sealed or flattened without using a flared glass stem which is used with a common incandescent lamp. In the halogen lamp, therefore, four lead-in wires connected with the filaments need be arranged in a straight line on a single sealing surface. Since the sealed beam lamp requires strict light distribution characteristic, the relative positions of the filaments in the bulb need be adjusted with high accuracy.
A conventional method for locating a pair of filaments at substantially the same height is as follows. First, two lead-in wires are fitted in a pair of lead-in wire holes formed in a single-connector mount head, and a filament coil is stretched between the tip ends of these lead-in wires to complete a desired mount, e.g. a mount for running beam. Then, after a mount for pass-by beam is manufactured in like manner, a double-conductor mount head having four lead-in wire holes arranged in a straight line is prepared. Then, the respective lead-in wires of the two mounts are transferred to this mount head so as to be located alternately. Thereafter, the lead-in wires are arranged in a straight line, and two filaments are located at substantially the same height.
However, the process for transferring the mounts separately manufactured on the single-conductor mount head to the double-conductor mount head depends largely on manual work, so that the working efficiency is too poor to enjoy mass production. Moreover, the manual work, which is low in reliability by nature, cannot ensure high-accuracy location of the filament coils, and is liable to cause variations in the mount shape.